Background: The HPTN 083 trial demonstrated superiority of HIV pre-exposure prophylaxis (PrEP) containing long-acting injectable cabotegravir (CAB) to daily oral tenofovir disoproxil fumarate/emtricitabine (TDF/FTC) among men who have sex with men (MSM). We compared the potential population-level impact of TDF/FTC and CAB among MSM in Atlanta, Georgia. Methods: An MSM HIV transmission model was calibrated to Atlanta-specific data on HIV prevalence and PrEP usage (percentage of uninfected MSM on PrEP), assuming only PrEP-indicated MSM used PrEP. CAB effectiveness (efficacy × adherence) of 91% was estimated using data from HPTN 083 and previous TDF/FTC trials. We estimated HIV infections averted over 5/10 years if TDF/FTC use were maintained, or if all TDF/FTC users switched to CAB in January 2022 (vs. no PrEP or continued TDF/FTC use). CAB scenarios with 10%/20% more users were also considered. Progress towards Ending the HIV Epidemic (EHE) goals (75%/90% fewer HIV infections in 2025/2030 vs. 2017) was estimated. Findings: We predicted TDF/FTC at current usage (∼28%) would avert 36.3% of new HIV infections (95% credible interval 25.6-48.7%) among all Atlanta MSM over 2022-2026 vs. no PrEP. Switching to CAB with similar usage may prevent 44.6% (33.2-56.6%) infections vs. no PrEP and 11.9% (5.2-20.2%) infections vs. continued TDF/FTC. Increasing CAB usage 20% could increase the incremental impact over TDF/FTC to 30.0% over 2022-2026, getting ∼60% towards reaching EHE goals (47%/54% fewer infections in 2025/2030). Reaching the 2030 EHE goal would require 93% CAB usage. Interpretation: If CAB effectiveness were like HPTN 083, CAB could prevent more infections than TDF/FTC at similar usage. Increased CAB usage could contribute substantially towards reaching EHE goals, but the usage required to meet EHE goals is unrealistic.